M809-series (M818) Air Brake Retrofit

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Trango

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Do you have any pics or a thread showing your modifications?
I wish I were as diligent or clean as you were. Sadly, I don't have anything as rigorous as what you've done. I don't even think I took any pictures. I recall doing the following:

- First off, I had already flipped my axle housing around, which put the tie rod in the front. I had done this when I built this vehicle, to put the pinion in the right place (passenger side of centerline) to engage the M35 transfer case, which I retained. Turning the whole axle around was far easier than pulling the hubs, then the shafts, and turning around the centersection, which also involves redrilling some mounting holes in the centersection. I have done that on M35 axles to relocate the pinion, and it is a bit onerous. Furthermore, I think I also achieved better pinion location by doing this "lazy" method, based on offset of the axle housing's banjo.
- Redrilling the brake spiders. The goal there was to locate the S-cam camshaft in the absolute "lowest" place in the knuckle, which happens to be just next to the top kingpin. I mean "lowest" not in terms of vertical height, but rather in terms of radial distance from axle centerline. Achieving that goal required that I drill a new series of holes out of phase. This pattern was easy to mark by using the spindle as a template, along with transfer punches to transfer the marks. I drilled these holes (in the 1/2+" thick casting!) using my mag-drill, which drills holes on par with reamed bores.
- Very light grinding / surfacing of that "low point" on the knuckle, where the camshaft passes, by no more than 1/8" or so. This helped clear that camshaft guide.
- Cutting and rewelding of the camshaft mount, to reclock the slack adjuster in a better location. This camshaft guide is already a fabricated part, which I rewelded with proper technique.
- Slightly notching the casting web on the steering knuckles (between main body and the tie rod mounting point) to clear the drums. Alternately, I could have turned down the drums, but my lathe only goes to 13" and I didn't yet have a mill. As another potential solution, I could have also spaced out the whole works.

In all, not a ton of compromises. I will try to take some pics later. Obviously, the internal stuff will be impossible to photograph from afar.

I got these brakes as part of a package deal. I scrapped the axles, with brakes, off an M54 that (decades ago) had the rear axles converted to air using an older system, with the front not wearing any brakes, acceptable as it was pre-'64 (or whatever the cut-off was for no front brakes on OTR trucks, can't remember). I believe the system was configured and sold by Memphis Equipment, but that was based on hearsay. And, having never compared 5 ton stock drums vs. these, I cannot be sure if these are matched to the spiders or if this is a creative reuse of stock drums, but I strongly suspect the former.

I bought all three axles, figuring that the commonality in the axle platform should allow me to take the brakes off one of the rear and put it on the front. Luckily, I was correct, even if it took some work.

I tied these into the existing air brake system for a 1994 Ford C8000 chassis, which lent the frame, engine, and air brake system to this most recent build.

As you know, the 16.5x7 brakes were (from memory) designed for a GVWR of up to 80k lbs. On a truck that weighs 15k, a heavy braking foot plus those systems will help you kiss the windshield.
 
Last edited:

Trango

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VERY GLAD to see you are still on here!

I'd also like to see pics if you have them....
:) I come on from time to time. I have been pretty busy with life and involved in other projects, including two other project vehicles. That said, the franken sheetmetal on this build is starting to bug me aesthetically, and I finally have (or at least think I have) the bandwidth to replace it with longer 5 ton stuff (I just have to find it, for a good price!).

Hope all is well.

I'll work on pics.
 
I wish I were as diligent or clean as you were. Sadly, I don't have anything as rigorous as what you've done. I don't even think I took any pictures. I recall doing the following:

- First off, I had already flipped my axle housing around, which put the tie rod in the front. I had done this when I built this vehicle, to put the pinion in the right place (passenger side of centerline) to engage the M35 transfer case, which I retained. Turning the whole axle around was far easier than pulling the hubs, then the shafts, and turning around the centersection, which also involves redrilling some mounting holes in the centersection. I have done that on M35 axles to relocate the pinion, and it is a bit onerous. Furthermore, I think I also achieved better pinion location by doing this "lazy" method, based on offset of the axle housing's banjo.
- Redrilling the brake spiders. The goal there was to locate the S-cam camshaft in the absolute "lowest" place in the knuckle, which happens to be just next to the top kingpin. I mean "lowest" not in terms of vertical height, but rather in terms of radial distance from axle centerline. Achieving that goal required that I drill a new series of holes out of phase. This pattern was easy to mark by using the spindle as a template, along with transfer punches to transfer the marks. I drilled these holes (in the 1/2+" thick casting!) using my mag-drill, which drills holes on par with reamed bores.
- Very light grinding / surfacing of that "low point" on the knuckle, where the camshaft passes, by no more than 1/8" or so. This helped clear that camshaft guide.
- Cutting and rewelding of the camshaft mount, to reclock the slack adjuster in a better location. This camshaft guide is already a fabricated part, which I rewelded with proper technique.
- Slightly notching the casting web on the steering knuckles (between main body and the tie rod mounting point) to clear the drums. Alternately, I could have turned down the drums, but my lathe only goes to 13" and I didn't yet have a mill. As another potential solution, I could have also spaced out the whole works.

In all, not a ton of compromises. I will try to take some pics later. Obviously, the internal stuff will be impossible to photograph from afar.

I got these brakes as part of a package deal. I scrapped the axles, with brakes, off an M54 that (decades ago) had the rear axles converted to air using an older system, with the front not wearing any brakes, acceptable as it was pre-'64 (or whatever the cut-off was for no front brakes on OTR trucks, can't remember). I believe the system was configured and sold by Memphis Equipment, but that was based on hearsay. And, having never compared 5 ton stock drums vs. these, I cannot be sure if these are matched to the spiders or if this is a creative reuse of stock drums, but I strongly suspect the former.

I bought all three axles, figuring that the commonality in the axle platform should allow me to take the brakes off one of the rear and put it on the front. Luckily, I was correct, even if it took some work.

I tied these into the existing air brake system for a 1994 Ford C8000 chassis, which lent the frame, engine, and air brake system to this most recent build.

As you know, the 16.5x7 brakes were (from memory) designed for a GVWR of up to 80k lbs. On a truck that weighs 15k, a heavy braking foot plus those systems will help you kiss the windshield.
Some helpful information here is you don't have to redrill holes on a 5ton to spin the centerchunk the bolt pettern is the same no matter which way you turn it unlike the 2.5ton. Also by putting the tierod on the front side you now have reversed your Ackerman Angle which affects the steering control of the vehicle. To correct it you can just swap the knuckles from one side of the housing to the other so the housing stays where you put it but the tierod is on the back once again giving it correct Ackerman Angle. The truck will turn better and will give less tire wear and will drive down the highway with less driver input.
 

Trango

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Here are the pics I discussed. First one shows notching of the web on the steering knuckle. Minor, but it needed to be done. I used a grinder, which was both the easiest and expeditious, and also left a curved gouge, which should not create too much of a stress riser.

The next picture shows the sectioning I had to accomplish on the slack adjuster housing tube. In that procedure, I cut out a "window" on the slack adjuster tube, and then replaced it with a much thinner (wall thickness) piece of tubing of the same ID. That allowed me to slide the slack adjuster tube closer to the knuckle. Longer term, I may add an additional mounting tab that ties into the two unused bolts that used to hold the boot guard, but that's far from the top of the priority stack.





This project is around 6 years old, so the componentry is dirty and there are a few cobwebs here and there. I assure the observer that it not only works, but is loads better than the stock braking on these trucks!
 

Trango

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Also by putting the tierod on the front side you now have reversed your Ackerman Angle which affects the steering control of the vehicle. To correct it you can just swap the knuckles from one side of the housing to the other so the housing stays where you put it but the tierod is on the back once again giving it correct Ackerman Angle. The truck will turn better and will give less tire wear and will drive down the highway with less driver input.
This is very intriguing, and something I did not consider. After all, most of my 4wd projects have had a front tie rod!

To be sure, I strongly, strongly doubt that I will undertake this project, especially with the extreme effort involved in tearing everything down and moreover because I prefer the airbrake cans on the aft side of the knuckle, but this is something certainly to watch for in the future. If steering effort or tire wear become undesirable, my priorities may shift. And, I will have a good basis for consideration, based on this post. Thanks!

Also, I seem to recall, several years ago, buying the adapters from you to put the M35a2 Transfer case into the otherwise 1710-yoked drivetrain. They have worked out brilliantly!
 

Trango

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By any chance Trango do you have the part #'s from your S cam front brakes?
I don't, aside from being spiders suitable for 16.5x7 series Q brakes. There is an outside chance that I have pictures on an old phone or hard drive, but the effort to explore that angle is months out, driven by a household desire to put together a file server, and we haven't even decided on a platform yet. Anyway, not to detail all the dependencies holding up that exploration, but if I find that information, I will post up.

That said, for reasons I've posted up about, the spider I used wasn't the ideal one. It would be better to find a drum package that put things a bit more outboard. Moreover, slotting that S-cam past the knuckle was really, really tight. Thinking outloud, those knuckles are potentially cast or nodular steel, and make take a weld, if it were possible to mill a better slot for the S-cam and route it through an integral cam-support (that is, integral to the knuckle).

Just thinking out loud. The implementation I did was not perfect, but works well enough.
 

Jakelc15

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Hanover Pa
I have a question for you brake savvy fellers. Second opinion is never a bad thing.

I want to convert to s cams on the rear of my truck(M818).
Same exact setup as myothersanm1.
But for the front, would it be acceptable to leave the juice brakes? Front brake air supply line plumbed into the airpack. In theory it should apply the brakes just as if it was being flat towed. Still giving me dual circuit and real parking brake.
What ya think?
 
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MyothersanM1

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I have a question for you brake savvy fellers. Second opinion is never a bad thing.

I want to convert to s cams on the rear of my truck(M818).
Same exact setup as myothersanm1.
But for the front, would it be acceptable to leave the juice brakes? Front brake air supply line plumbed into the airpack. In theory it should apply the brakes just as if it was being flat towed. Still giving me dual circuit and real parking brake.
What ya think?
I don't about using the original set up in conjunction with full air air brakes. You still have to actuate the master cylinder. I know Memphis Equipment does their conversions using an air chamber connected to a master cylinder to the front juice brakes. Whether it is routed into the air pack still, I don't know. Call them and bend their brains. I'm sure they will help you out.
100_6973.jpg
Photo credit: Steel Soldiers member OPCOM

Using the M939/M939A1-series front brakes was the simplest solution for me, plus I am not mixing two distinct types of braking systems. Luckily, I was able to source all the parts for a reasonable price. I just had to do all the removal work...I think my back is still aching!
 

Jakelc15

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OK. Thanks. I didn't know Memphis equipment had a similar setup. I thought about using a air chamber to push the master cylinder or using a chamber and cylinder from an m105 or similar. Front 939 wedges would be best though.
For some reason people think 939 brakes are made of gold!
 

MyothersanM1

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For some reason people think 939 brakes are made of gold!
Yeah, I don't get that! Trick is to find a donor truck and do the work yourself. All you need is the spiders, drums, hubs and air chambers. Those will only work together and do not interchange with M809-series parts, but are common to the steer axle on all three truck series except for the M939A2-series. Bearings and axle caps are interchangeable. Shoes, air diaphragms and all seals (hub and plunger) should be changed and are obtainable fairly easily and economically.


Did you compile this? Good work! I also listed all the part numbers earlier in the thread.

http://www.steelsoldiers.com/showthread.php?140055-M809-series-(M818)-Air-Brake-Retrofit/page2
Post #17
 

charlesmann

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i tried some google searching and couldnt find anything. but why would the brake set up from a mack axle not work on 5 tn rockwell? its been 2o yrs since i wrenched on big truck, and only did that for about 8 months, but if men serves me correct, the r and rd model mack axles look the same as the rockwell's. am i completely wrong? i was wanting to swap from wedge (never heard of wedge brakes till i went to RRAD for a 6wk crash course on MRAP repair) to S cam, bc of the nightmare to tear down the mil style axles and mess with the wedges. id rather swap to s cams, but if for the 900 a2 series trucks are i/b style drums (hub and drum come off and go on together) then doing the swap in the short near future isn't worth the $$ and hassle to change to S cams.

any guidance\, thoughts as to the similarities of the mack v. rockwell set up?
 
i tried some google searching and couldnt find anything. but why would the brake set up from a mack axle not work on 5 tn rockwell? its been 2o yrs since i wrenched on big truck, and only did that for about 8 months, but if men serves me correct, the r and rd model mack axles look the same as the rockwell's. am i completely wrong? i was wanting to swap from wedge (never heard of wedge brakes till i went to RRAD for a 6wk crash course on MRAP repair) to S cam, bc of the nightmare to tear down the mil style axles and mess with the wedges. id rather swap to s cams, but if for the 900 a2 series trucks are i/b style drums (hub and drum come off and go on together) then doing the swap in the short near future isn't worth the $$ and hassle to change to S cams.

any guidance\, thoughts as to the similarities of the mack v. rockwell set up?
I am working with Myothersanm1 on outboard drums for the S cam and wedge brakes as we speak , We will post our success or failure in the near future.
We are working with M809/939A1 hubs the A2 drums are already outboard, and we are using easy to get modern commercial drums.
 
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charlesmann

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so would the civi s cam system work so those wedge sys can be sent to a forge and turned into something like a knife, or a hammer to beat the next set of wedge brakes out with?
 
so would the civi s cam system work so those wedge sys can be sent to a forge and turned into something like a knife, or a hammer to beat the next set of wedge brakes out with?
From everything I have read and my experience so far there is nothing wrong with wedge air brakes ,you just need to maintain them properly . Yes S cam brakes are easier to work with but an expensive change and so far not easily done in the front .In my opinion outboard drums will make working on the wedge brakes a lot easier and that's what I am going to work towards .
 

MyothersanM1

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so would the civi s cam system work so those wedge sys can be sent to a forge and turned into something like a knife, or a hammer to beat the next set of wedge brakes out with?
Yes, on the rears. I bought all my parts in a kit. If you piece the parts together you are going to find the spiders are the hardest parts to obtain.
I have not nor have I found anyone who has found a viable alternative in an s-cam to retrofit the Rockwell top-loader steer axle.
 

charlesmann

Member
30
5
8
Location
Temple, Tx
From everything I have read and my experience so far there is nothing wrong with wedge air brakes ,you just need to maintain them properly . Yes S cam brakes are easier to work with but an expensive change and so far not easily done in the front .In my opinion outboard drums will make working on the wedge brakes a lot easier and that's what I am going to work towards .
I first saw/dealt with wedge brakes when i went through the MRAP school at RRAD back in 2012. we only tore down an oshkosh MATV brake sys, and after the crap with that, i never wanted to mess with wedges again. i'll tear into an axle just s&g to assess the wear of the liners and how mechanically sound the sys is. if its an easy deal, cool, i'll stay with the wedges.

Glengineer, you are just a ferry ride east of me right now. I'm in port alberni on my first hitch with my new acft employer. if I'm coming back up my next, i will see about flying in a day earlier and linking up with you.
 
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